Oil well treatment to overcome water coning



June 11, 1963 J, c, ALLEN OIL WELL TREATMENT TO OVERCOME WATER CONING Filed July 14, 1958 W M W n w v I f ZI IIIIA IVIIIIAI I/IIA I IIIIA IV/l/II/I/I/II/ United States This invention relates to the production of petroleum hydrocarbons from a subsurface reservoir. More particularly, this invention relates to the production of liquid petroleum hydrocarbons from a subsurface reservoir which overlays a substantially water-saturated, water-producing formation. Still more particularly, this invention relates to a method for overcoming water-coming which sometimes results during the production of petroleum hydrocarbons from a petroleum-producing formation which overlays a substantially water-saturated formation.

Water-coming is a term given to the mechanism underlying the entry of bottom waters into petroleum or oilproducing wells. Petroleum hydrocarbons are often produced from subsurface formations which overlay a substantially water-saturated formation. Under static conditions the water, having a greater density than the liquid petroleum, remains at the bottom of the petroleum-producing formation. At high rates of production of petroleum, however, the upper surface of the substantially water-saturated formation rises due to the increased flow of liquid petroleum into the well bore which extends into the liquid petroleum-producing formation immediately adjacent and above the substantially water-saturated formation. The rise of water into the petroleum-producing formation and into the well bore represents a dynamic elfect in which the upward directed pressure gradients associated with the flow of the petroleum into the producing well bore are able to balance the hydrostatic head of the resulting elevated water column.

Various methods have been suggested heretofore to eliminate or to reduce the water-coning phenomenon. These methods have included reducing the well pentration into the liquid petroleum-producing formation so that higher production rates are possible Without at the same time experiencing an excessive production of water therewith. Another method which has been suggested is to bottom the producing well into a substantially waterimpermeable formation. These indicated methods, however, cannot be successfully employed in all instances to eliminate or reduce water-coming. Certain underground liquid petroleum-producing formations are only a relatively few feet in thickness. Accordingly, reducing the well bore penetration into such a formation would unduly restrict the recovery of liquid petroleum therefrom. Other liquid petroleum formations do not have associated therewith an immediately underlying water-impermeable formation.

It is an object of this invention to provide an im proved method for the recovery of petroleum hydrocarbons from subsurface petroleum-producing formations.

It is another object of this invention to provide an improved method for the recovery of liquid petroleum hydrocarbons from a liquid petroleum-producing formation which overlays a substantially water-saturated formation.

It is still another object of this invention to provide a method of preventing and/ or reducing water-coning as evidenced by the production of a relatively large amount of water with respect to produced liquid petroleum during the production of liquid petroleum from a well bore extending into a liquid petroleum-producing formation and an adjacent underlying water-producing formation.

It is still another object of this invention to provide an improved method of well completion wherein the well bore extends into a liquid petroleum-producing formation which overlays a water-producing formation.

These and other objects of this invention and how they are accomplished will become apparent with reference to the accompanying drawing wherein:

FIG. 1 schematically illustrates the water-coning phenomenon; and

FIG. 2 schematically illustrates a method in accordance with this invention for overcoming water-coming.

In accordance with this invention water-coning is overcome by injecting into the water-producing formation giving rise to the water-coming phenomenon a substantial amount of gas. As the gas is injected into the waterproducing formation, the Water filling the pores or interstices of the formation is displaced and forced back by the injected gas. The injection of gas into the Wat rproducing formation is continued until the water has been displaced a substantial radial distance, e.g., at least about 5 feet, preferably at least about 20 feet, from the point of injection, which is conveniently the well bore itself. Initially, the pores of the water-producing formation adjacent or in the vicinity of the well bore are usually substantially saturated with water, i.e., 100 percent occupied by water. After the injection of gas the water saturation of the producing formation in the Zone of gas injection thereinto is substantially reduced, for example, a water saturation in the range 50%, the gas saturation being in the range 550%.

Subsequent to the injection of gas into the water-producing formation there is introduced into the thus-treated formation a solvent liquid containing asphaltic material dissolved or suspended therein. Upon the injection of the solvent liquid into the gas treated portion of the water-producing formation deposition of asphaltic material within the water-producing formation in the immediate vicinity of the well bore occurs. The precipitation of asphaltic material from the solvent liquid containing the same is effected by vaporization of the solvent into the gas-treated water-producing formation and/ or by a deasphalting effect of the previously injected gas upon the subsequently injected solvent liquid asphalt-containing solution. Thereafter, additional solvent liquid is introduced into the formation to redissolve and/ or disperse the thus-precipitated asphaltic material outwardly into the gas-treated portion of the water-producing formation to effect a plugging in depth in that portion of the formation in the vicinity of the well bore due to extended deposition or reprecipitation of asphaltic material within the thus-treated portion of the water-producing formation for a substantial distance outwardly from the well bore. As a result of the dispersion and/ or reprecipitation of the initially precipitated asphaltic material the porosity of the thus-treated portion of the water producing formation is substantially reduced. Also as a result of this plugging action or reduction in porosity, the water permeability of the formation is substantially reduced. Subsequently petroleum production is then resumed from the overlying petroleum-producing formation via the well bore. Since the underlying water-producing formation from which the water-coming originates is now substantially plugged and evidences a substantially reduced water permeability for a considerable distance surrounding the well bore, the production of petroleum from the overlying petroleumproducing formation can be carried out at relatively high rates of production without undue danger of water-coiling or excessive production of water with the produced petroleum. Since the deposited asphaltic materials are water insoluble the above-indicated treatment of the waterproducing formation to eliminate and/or inhibit waterconing is permanent in nature.

The term asphaltic material as used herein means resinous, asphaltic, carbenic hydrocarbons r asphalts, pitches and tars of a plastic or solid nature, found in crude petroleum and the like or petroleum fractions, and effective to plug the interstitial voids of the water-producing formation.

Any suitable liquid solvent for asphaltic material may be employed in the practice of this invention. Particularly suitable for use in the practice of this invention are asphaltic crudes or crude oil or fractions thereof such as may be recovered from the petroleum-producing formation overlying the water-producing formation undergoing treatment in accordance with this invention, containing asphaltic material dissolved therein. Other liquid asphaltic solvents or carriers useful in the practice of this invention include carbon tetrachloride, aromatic hydrocarbons such as benzene, xylene and the like, gas oils, kerosenes and higher boiling distillate fractions, etc. in gen eral, the liquid solvent or carrier for asphaltic material employed in the practice of this invention may comprise any liquid having substantial solubility or solvent power for asphaltic material and which, desirably, is also compatible with the liquid petroleum in the overlying petroleum-producing formation.

Various gases may be employed in the practice of this invention. Suitable gases include natural gas, usually associated with and dissolved in the liquid petroleumproducing formation and which is recovered therefrom by suitable means, such as a gas-liquid separator at the surface. It is preferred that the injected natural gas be dry, that is, having had its natural gasoline content stripped therefrom. Another gas which may be employed in the practice of this invention is air. Still another gas which is suitable in the practice of this invention is a gaseous mixture of combustion products such as a flue gas and the like, usually containing nitrogen, carbon dioxide and other gases in varying amounts. Normally gaseous hydrocarbons such as methane, ethane, propane, n-butane and/or isobutane, or mixtures thereof are particularly useful in the practice of this invention since these normally gaseous hydrocarbons exhibit a deasphalting effect upon liquid asphalt-containing oils and crudes in contact therewith.

Referring now to FIG. 1 of the drawing which schematically illustrates the water-coming phenomenon, a subsurface liquid petroleum-producing formation is indicated at 11. An immediately underlying, saturated, water-producing formation is indicated at 12. A well bore 13 extends into the liquid petroleum-producing formation 11 and the water-producing formation 12. A production casing '14 is provided with perforations 15 Within the petroleum-producing formation 11. Under static conditions or at a relatively low rate of liquid petroleum production from the liquid petroleum formation 11, the upper surface of the water-producing formation is located at about the position indicated by the dashed line 16. At relatively high rates of production, however, because of the upward directed pressure gradients associated with the flow of liquid petroleum into perforations 15, the water table rises to the extent it is balanced by these upward directed pressure gradients. As the water table rises, as indicated by solid line 17, to the area of production of liquid petroleum hydrocarbons, water is produced by the lowermost perforations 15 of casing 14. At still greater rates of production of liquid petroleum from formation 11, the water table continues to rise and there results a greater production of water relative to the amount of produced liquid hydrocarbons. The abovedescribed phenomenon is commonly known as waterconing.

Referring now to FIG. 2 of the drawing, there is schematically illustrated therein a method according to this invention for preventing and/or reducing water-coming. The same reference numerals have been employed in FIG. 2 as were employed in FIG. 1 for reasons of clarity and ease of understanding. As indicated in FIG. 2, well bore 13 provided with casing 14 extends into liquid petroleum-producing formation 11 which overlays waterproducing formation 12. In order to prevent and/ or reduce water-coming when the production of liquid petroleum is commenced through perforations 15 of casing 14 within the petroleum-producing formation 11, packing :18 is inserted within casing 14 at about the normal interface of the formations 11 and 12, as indicated by dashed line 16. After the packing 18 has been installed, a gas such as natural gas, e.g., methane or propane, is injected via conduit 19 into the formation 12 via perforations 20 in casing 14. The injection of gas into formation 12 is continued until the water has been displaced within formation 12 for a substantial radial distance surrounding that portion of well bore 13 within formation 12, to the extent indicated by dashed line 21. After a sufficient amount of gas has been injected to displace the water from around the well here 13 immediately adjacent the liquid petroleum-producing formation 11, the injection of gas is stopped.

Following the injection of gas into the water-producing formation 12 via perforations 20 there is introduced into water-producing formation 12 via tubing 19 and perforations 20 an oil containing asphaltic material dissolved or suspended therein. Upon the introduction of oil into the thus gas-treated portion of the water-producing formation 12 deasphalting or precipitation of asphaltic material occurs in the immediate vicinity of the well bore. After a sulficient amount of asphaltic material has been thus deposited within formation 12 in the immediate vicinity of the well bore additional oil or asphaltic solvent is introduced in the formation to redissolve the thus-precipitated asphaltic material and to disperse and reprecipitate the asphaltic material outwardly into formation 12 for a substantial distance outwardly from the well bore. As a result of this operation the formation is thus treated in depth for a substantial distance outwardly from the well bore. Subsequently production of petroleum is then resumed from petroleum-producing formation 11 via perforations 15. Since the underlying portion of formation 12 is now substantially plugged with the asphaltic material so that the water permeability thereof is substantially reduced the production of petroleum from petroleum-producing formation 1 1 can be resumed at substantial rates of production without undue danger of water-coming.

In the above-indicated embodiment of this invention wherein an oil or hydrocarbon solution or suspension of asphaltic material is employed the asphaltic material is deposited within the interstitial non-wetting or funicular space of the thus-treated water-producing formation, i.e., that portion of the formation which would normally be occupied by oil or the non-wetting phase.

In accordance with another embodiment of the practice of this invention the treating solution comprising asphaltic material dissolved therein is an oil-in-water suspension or emulsion wherein the oil contains the asphaltic material dissolved or suspended therein. In the practice of this embodiment of the invention since the treating solution is an oil-in-water suspension the treating solution would occupy that portion of the formation normally occupied by the water or wetting phase. Accordingly, following the injection of the treating solution containing asphaltic oil-in-water emulsion deasphalting or precipitation of the asphaltic material due to contact with the previously injected gas would occur in the water phase immediately adjacent the rock matrix and in the most minute interstitial voids of the formation. Upon resumption of petroleum production from the overlying petroleum-producing formation these asphaltic solids would tend to move toward the well bore and asphaltic agglomerates would build up within the interstitial wetting phase rather than in the non-wetting phase or funicular interstitial space of the formation. The formation of asphaltic agglomerates in the wetting phase and region of the formation leads to more eflicient plugging and in some instances to actual cementation of the thus-deposited asphaltic material to the formation itself, thereby effecting a; lmore eifective plugging and reduction in water permeaiity.

Further explanatory of the practice of this invention, a concentrated solution of asphalt in CCl (23% by wt. asphalt) was introduced into contact with a typical gaseous mixture produced from a Gulf Coat condensate reservoir. The gaseous mixture comprising separator gas and separator liquid was at a pressure of 5900 p.s.i.g. and a temperature of 274 F. Upon injection, asphalt precipitation immediately occurred. The solid, precipitated asphalt was free from gloss and tackiness which characterized the asphalt employed to form the solution which was injected, and the precipitated asphalt was highly effective as a plugging material.

The practice of this invention is applicable not only to newly-drilled wells but is also applicable to previously drilled wells which are producing a considerable amount of water due to the phenomenon of water-coming. In previously drilled producing wells which exhibit an unduly large amount of water production due to waterconing the practice of this invention may be as follows.

The well is shut in for a period of time necessary to promote the establishment of equilibrium conditions in the subsurface producing formations. This period of time, depending upon various circumstances, may be three days to a month, more or less. Then a gas is injected into the water-producing formation immediately adjacent the liquid petroleum-producing formation in the vicinity of the well bore. This can be done by perforating the production casing in the water-producing zone and injecting gas thereinto. After a suflicient amount of gas has been injected to force the water in the formation a substantial radial distance outwardly from the well bore at the point of injection, gas injection is stopped and the Well treated by injection of an asphaltic containing liquid thereinto as indicated with respect to FIG. 2 of the drawing.

As will be apparent to those skilled in the art, many substitutions, alterations or omissions are possible without departing from the spirit or scope of this invention.

I claim:

1. A method of treating a well to inhibit water-coming during the production of oil from an oil-producing formation adjacent an underlying water-producing formation via a well bore extending through said oil-producing formation which comprises introducing a gas via said well bore into said water-producing formation in an amount sufficient to force water in said water-producing formation a substantial distance outwardly from said well bore adjacent said oil-producing formation, subsequently introducing via said well bore into that portion of said water-producing formation into which said gas has been introduced solvent liquid containing asphaltic material dissolved therein to effect vaporization of at least a portion of said solvent liquid and to effect precipitation of at least a portion of said asphaltic material contained in said solvent liquid, subsequently introducing solvent liquid substantially free of asphaltic material dissolved therein via said well bore into the thus-treated portion of said water-producing formation to force the remaining first introduced solvent liquid outwardly further into said waterproducing formation and to redissolve and reprecipitate the aforementioned precipitated asphaltic material thereby plugging a substantial portion of the thus-treated waterproducing formation outward from said well bore and substantially reducing the water permeability thereof, and subsequently resuming production of oil via said well bore from said oil-producing formation.

2. A method of treating a well bore which penetrates an oil-producing formation and into an adjacent underlying water-producing formation which comprises introducing via said well bore into said water-producing formation adjacent said oil-producing formation a normally gaseous hydrocarbon in gaseous state in an amount sufficient to force water in said water-producing formation a substantial distance outwardly from said well bore, subsequently introducing Via said well bore into the thustreated portion of said water-producing formation an oil solution containing asphaltic material dissolved therein to contact the previously introduced normally gaseous hydrocarbon introduced into said water-producing formation thereby tending to precipitate at least a portion of said asphaltic material within the thus-treated portion of the water-producing formation in the zone thereof immediately surrounding said well bore, subsequently introducing via said well bore oil to effect dissolution of precipitated asphaltic material and to move the redissolved asphaltic material outwardly from said well bore into the said thus-treated portion of the formation to cause said redissolved asphaltic material to be reprecipitated therein at a location within said water-producing formation removed from said well bore and resuming pro duction of petroleum via said well bore from said oilproducing formation.

3. A method of treating a well bore which penetrates an oil-producing formation and into an adjacent underlying water-producing formation which comprises introducing via said well bore into said water-producing formation adjacent saidoil-producing formation a normally gaseous hydrocarbon in gaseous state in an amount sufficient to force the water in said water-producing formation a substantial distance outwardly from said well bore, subsequently introducing via said well bore into the thustreated zone of said water-producing formation an oilin-water emulsion, said oil containing dissolved therein asphaltic material, permitting the thus-introduced oil-inwater emulsion to remain in contact within the thustreated portion of said formation with the previously introduced normally gaseous hydrocarbon to effect deasphalting of the oil in the oil-in-water emulsion thus introduced to cause asphalt to be precipitated from said emulsion within said formation and subsequently resuming production of petroleum via said well bore from said oil-producing formation.

4. A method of inhibiting water coning in a well wherein oil is produced from an oil-containing formation penetrated by a well bore and wherein said well bore also penetrates into an adjacent, underlying water-producing formation which comprises introducing via said well bore into said water-producing formation adjacent said oilproducing formation a normally gaseous hydrocarbon in gaseous state to substantially reduce the water saturation within the water-producing formation in a zone therein immediately surrounding said well bore, introducing into said zone of said water-producing formation an oil solution containing asphaltic material dissolved therein whereby said asphaltic material is precipitated from said solution within said formation in said zone immediately adjacent said well bore, subsequently introducing via said well bore into said zone of said water-producing formation oil in an amount sudlicient to redissolve the previously precipitated asphaltic material from immediately adjacent said well bore and to move and to reprecipitate said asphaltic material outwardly into said zone thereby effecting a redistribution of precipitated asphaltic material within said zone in said water-producing formation whereby a substantial portion of said zone has its porosity reduced due to the precipitation of asphaltic material therein and subsequently resuming production of oil from said oil-producing formation via said well bore.

5. A method of reducing water-coiling, as evidenced by the production of a relatively large amount of water with respect to produced liquid petroleum, which is experienced during the production of liquid petroleum from a well bore extending through a subsurface liquid petroleum-producing formation and into an adjacent underlying water-producing formation which comprises halting production of liquid petroleum from said well bore to promote the attainment of equilibrium conditions in the aforesaid subsurface formations, injecting via said well bore into said water-producing formation adjacent said petroleum-producing formation surrounding said well bore an amount of gas sufficient to force the water in said water-producing formation a substantial distance outwardly from said well bore, subsequently introducing into said water-producing formation into that portion thereof surrounding said well bore containing the injected gas a solution containing asphaltic material dissolved therein whereby asphaltic material is deposited in a zone surrounding said well how in the thus-treated water-producing formation due to vaporization of solvent from said solution, thereupon introducing additional solvent substantially free of asphaltic material via said well here into the thus-treated portion of the water-producing formation to dissolve the precipitated asphaltic material from the zone therein immediately surrounding said well bore and to move and reprecipitate this asphaltic material out- Wardly into the treated portion of said water-producing formation from said well bore and thereafter resuming production of liquid petroleum from said liquid petroleum-producing formation via said well bore.

6. A method in accordance with claim wherein the gas injected into the water-producing formation is natural gas.

7. A method in accordance with claim 5 wherein said solution containing asphaltic material dissolved therein comprises benzene as a solvent for said asphaltic material.

8. A method in accordance with claim 5 wherein said solution containing asphaltic material contains carbon tetrachloride as the solvent for said asphaltic material.

9. A method in accordance with claim 5 wherein said solution containing asphaltic material dissolved therein consists essentially of an oi'l-in-water emulsion wherein the oil phase of the emulsion dispersed in the continuous water phase contains asphaltic material dissolved therein.

10. A method in accordance with claim 5 wherein the solution of asphaltic material introduced into the waterproducing formation comprises an oil-in-water emulsion wherein the oil phase of the emulsion comprises a liquid hydrocarbon solvent for asphalt containing asphaltic material dissolved therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,032,826 Ambrose et a1 Mar. 3, 1936 2,053,285 Grebe Sept. 8, 1936 2,713,906 Allen July 26, 1955 2,779,415 Howard Ian. 29, 1957 2,779,416 Clark Jan. 29, 1957 2,784,787 Matthews et al Mar. 12, 1957 2,788,855 Peterson Apr. 16, 1957 2,801,699 Sayre Aug. 6, 1957 2,805,720 Wiegand Sept. 10, 1957 2,859,820 Trott Nov. 11, 1958 2,865,453 Widmyer Dec. 23, 1958 2,896,717 Howard July 28, 1959 2,923,356 Glass et al Feb. 2, 1960 

1. A METHOD OF TREATING A WELL TO INHIBIT WATER CONING DURING THE PRODUCTION OF OIL FROM AN OIL-PRODUCING FORMAMATION ADJACENT AN UNDERLYING WATER-PRODUCING FORMATION VIA A WELL BORE EXTENDING THROUGH SAID OIL-PRODUCING FORMATION WHICH COMPRISES INTRODUCING A GAS VIA SAID WELL BORE INTO SAID WATER-PRODUCING FORMATION IN AN AMOUNT SUFFICIENT TO FORCE WATER IN SAID WATER-PRODUCING FORMATION A SUBSTANTIAL DISTANCE OUTWARDLY FROM SAID WELL BORE ADJACENT SAID OIL-PRODUCING FORMATION, SUBSEQUENTLY INTRODUCING VIA SAID WELL BORE INTO THAT PORTION OF SAID WATER-PRODUCING FORMATION INTO WHICH SAID GAS HAS BEEN INTRODUCED SOLVENT LIQUID CONTAINING ASPHALTIC MATERIAL DISSOLVED THEREIN TO EFFECT VAPORIZATION OF AT LEAST A PORTION OF SAID SOLVENT LIQUID AND TO EFFECT PRECIPITATION OF 